London: In what is being claimed as a major breakthrough, scientists have regrown bone and cartilage from fat cells and muscle tissue taken from a patient and then implanting them at the site of the injury.

An international team, led by Harvard Medical School, has achieved the feat of converting muscle and fat cells into cartilage and then bone in rodents by using a special form of
gene therapy.

Tests in the rodents showed that the implanted muscle
and fat rapidly caused a bridge to form between broken bones
within days. The bones were found to have returned to full
strength within eight weeks of the injury.

It can typically take broken bones in humans several
months to heal, according to the scientists, who said that the
new technology could dramatically speed up the time it takes
to heal knee injuries, `The Daily Telegraph` reported.

"Further development of these methods should provide
ways to heal bone and cartilage more expeditiously, and at
lower cost, that is presently possible.

"Those receiving gene-activated muscle underwent rapid
healing, with evidence of bridging as early as 10 days after
implantation and restoration of full strength by eight weeks,"
Prof Chris Evans, who led the team, said.

The gene therapy technique takes advantage of a
defect that is found in patients suffering from an extremely
rare disease, known as fibrodysplasia ossificans progressiva,
which causes bone to form in the patients` muscles.

These patients carry a variation of a gene that codes
for a molecule called bone morphogenetic protein.

The scientists found that they could introduce this
defective gene into healthy muscle and fat using a virus that
inserts the gene into the cell`s DNA. When the muscle or fat
is then implanted into the site of a broken bone, it starts
to convert to bone.

In rats, they found that treated muscle was faster and more effective at healing than fat. The treated fat also
improved healing.

Judith Hoyland, a researcher in regenerative medicine
who was also involved in the project, said: "We showed that
cells implanted into the animal did actually migrate to the
injured tissue and were forming bone."

The scientists added that the modified muscle and fat
implants not only create new bone, but they also promote the
body`s own healing process causing it to grow new bone.

Pilot tests in rabbits also showed the implants
could repair damaged knee cartilage. They are now planning to
conduct further animal trials before attempting the technique
in human patients.

The findings have been published in the `European
Cells and Materials` journal.